From: on behalf of Panel Registry Subject: FW: TNG registration of ...

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• Remain stable and capable of conveying peak flows, during
its indefinitely long life, and
• Provide water of appropriate thermal character for trout.
The documents prepared do not, in my opinion, provide
adequate explanation of the design that will allow the channel to
collect ground water while preventing entrained water from leaving
it. The project documents indicate that the channel may be lined in
some sections to make it impervious. If this is the case, how might
sub-surface water enter such a structure?
The channel is proposed to be one meter across the bottom
with sloping sides 1:1.5, with a cross-sectional area of about 2.6
square meters. It is stated that it will withstand 1:100 year floods.
However, adequate information on flood return times is not given in
the Fisheries Compensation Plan. The plan indicates that the average
flow, during May, through the HC at the 4, 5, 6, and 7 km locations,
will be 0.330, 0.413, 0.459, and 0.578 cubic meters per second
respectively. These data are not accompanied by information on
flow extremes. What are the potential flow levels and water
velocities in, for example, 10, 50, 100, and year return period
events? In my opinion there is risk and uncertainty in this part of the
plan.
The information on the thermal characteristics of water flowing
north to south through the HC, and thus exposed to radiant energy
at the peak of day, is inadequate. The length is 10.8 km., flow
volumes are relatively low in the north end of the channel, and the
banks are open along its length. Notwithstanding the fact that main
flows occur in May, there is potential for water warming along the
channel. Water temperature questions in regard to the HC are
important, because warming effects in the channel will be additive
to those in the HCRP.
The Headwater Channel Retention Pond
The 26.1 ha HCRP is intended to store water, which will
be released into the spawning and rearing channel during the spring
and summer incubation and early rearing period. The maximum
depth of the pond is to be 5 m. The morphometric data for the